Metabolic engineering of for production of non-natural acetins from glycerol

Mono-, di- and triacetin are three glycerol esters which are usually synthesized via costly and environmentally unfriendly chemical synthesis methods. Here, Escherichia coli is metabolically engineered for the production of mono-, di- and triacetin using glycerol as a substrate. First, a novel biosynthetic route of mono- and diacetin is established by overexpression of a native enzyme, maltose O -acetyltransferase (MAA). Next, the biosynthetic pathway is extended to produce a mixture of mono-, di- and triacetin by overexpression of chloramphenicol- O -acetyltransferase (CAT). By successive strategies, including heterologous gene expression, metabolic engineering, and culture optimization, a recombinant E. coli is enabled to produce more than 27 g L −1 of a mixture of mono-, di- and triacetin in shake flask cultures, which is a >650-fold increase over the initial production of 0.04 g L −1 . In vitro studies confirm the acetylation of glycerol to mono- and diacetin by MAA, and the additional acetylation to triacetin by CAT. When crude glycerol is used as a substrate, the engineered strain produced a total of 25.9 g L −1 of the acetin mixture, about the same as that achieved from pure glycerol. To our knowledge, this is the first successful report of microbial production of the artificial chemicals, acetins. Development of bioconversion technology for efficient conversion of crude glycerol to non-natural acetins.